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Iron Metabolism

When we eat iron, we generally get it in one of two forms: elemental iron or heme (from meat). In the intestine (proximal duodenum to be precise) the iron is either absorbed or actively transferred in. Iron is transported in the blood bound to transferrin and is stored in the liver bound to ferritin. This is why ferritin is measured when assessing iron stores.

Though most of the time you can make the diagnosis of iron deficiency anemia by assessing the patient’s history and CBC (microcytic anemia), you can also do an “iron study” that looks at the following:

Ferritin: indicator of iron stores, will be reduced in iron deficiency anemia

Serum iron (SI): decreased in iron deficiency anemia

Total iron binding capacity (TIBC): measures transferrin, this is elevated when iron is low

% saturation = SI/TIBC x 100, reduced in iron deficiency anemia

It’s good to keep the other causes of microcytic anemia in mind. To remember you can use the mnemonic TAILS

Thalassemia

Anemia of chronic disease

Iron deficiency

Lead poisoning

Sideroblastic anemia

*I realize that using “anemia” as the A is a little bit of a cop out in a mnemonic devoted to anemia, but I wasn’t the one who came up with it and TCILS just isn’t as easy to remember.